With the development of the thin film field effect transistor liquid crystal display (TFT-LCD) technology and the progress in the industrial technologies, the production cost of liquid crystal displays is continuously reduced and the manufacturing process thereof is increasingly improved, thus they have become a mainstream technology in the flat panel display field in place of cathode ray tube displays. TFT-LCD displays have become ideal display devices due to their advantages such as small size, low power consumption, no radiation, and so on. The basic structure of a TFT-LCD comprises an array substrate, a color filter substrate, and a liquid crystal layer (LC) sandwiched between the two substrates. A polyimide film layer (alignment film layer) having an orientation effect on the liquid crystals is arranged on the surfaces of the array substrate and the color filter substrate. Taking the existing twisted nematic (TN) type TFT-LCD as an example, the TFT structure is formed by depositing a gate electrode, a common electrode, a first insulating layer, an active layer, a source/drain electrode, a second insulating layer, and a pixel electrode on a glass substrate successively, the gate electrode and the common electrode are arranged in the same layer.